netbsd-4, drm directory and files.pci

Hello,
I'm running netbsd-4/amd64.
As I noticed that "sys/dev/pci/drm" had things in it, I added the relevant
device line to my kernel config and tried to compile it. Of course, it
failed ;-( As I understand the error, this is because "sys/dev/pci/files.pci"
has no reference for it.
Is that expected ?
If so, why having half the code in the branch ?
TIA,
Jo